Türkiye Jeoloji Bülteni

A Study on Regional Metamorphism of Northeastern Part of Central Anatolian Massif (Akdağmadeni, Yozgat)

Abstract: In this paper, some data related to the regional metamorphism, obtained during a study on mineralization around a graniteintrusion in the east of Akdağ madeni (Yozgat Î35-c2 sheets), are presented.The study area has a southwest plunging anticlinal structure with a granite intrusion in the center. Indications of contact metamorphism in the rock groups, namely calcsilicatic gneiss, marble, quartzite/quartzschist, gneiss and amphibolite around the graniteintrusion, are clearly seen. Calcite+diopside+scapolite+plagioclase+sphene paragenesis in the calcsilicatic gneisses, and sillimanite+orthoclase paragenesis in the gneisses are observed. Reddish-brown pleochroism color in biotites of the gneisses, and brownishgreen pleochroism color in hornblendes of the amphibolites were determined. All the mineral groups which exist in the abovementioned rocks indicate a high degree of regional metamorphism in the area.On the basis of the petrological data obtained in this study, it is not possible, as it was done by some previous investigtors, todivide the regional metamorphic rocks as upper and lower series and to map them as such. It is not also possible to state thatinitially a high degree of metamorphism, has been effective in the area.In the study area, a carbonaceous series with about 1500 m thickness wnich includes some pelitic layers, had been subjected to anintermediate pressure/high temperature metamorphism, as it is in the vicinity of Kırşehir. It was not possible to differentiate anymetamorphic zoning in the study area; and it is accepted that all the rocks in the area belong to a single metamorphic zone.